Is a Single Nucleotide Polymorphism Marker in the Cholecystokinin A Receptor Gene Practically Suitable for Improving the Growth Traits of Hinai-jidori Chickens?

We have previously reported a significant association between the single-nucleotide polymorphism (SNP; g.420 C>A) in the cholecystokinin type A receptor gene (CCKAR) and the growth traits of Hinai-dori, a breed of chicken that is indigenous to Japan. Moreover, we have demonstrated that the minor allele of this SNP improved the growth rate in a low-growth line of the Hinai-dori breed. Hence, in the present study, we verified the association between this SNP and the growth traits of the Hinai-jidori chicken: a cross between a Hinai-dori sire and Rhode Island Red dam. In addition, we verified whether the growth rate was improved in Hinai-jidori chickens produced from the parent stocks in which the SNP A/A genotype was fixed by selection (improved Hinai-jidori chickens). The Hinai-jidori female chicks at 4 weeks of age, were subdivided into three genotypic groups (A/A, A/C, and C/C), with 20 chicks in each group, and reared in an open-sided poultry shed until 23 weeks of age. The results showed that the body weight at 23 weeks of age and the average daily gain after 14 weeks of age were significantly higher in group A/A than in group C/C. Subsequently, the improved and the conventional Hinai-jidori chickens were reared until they reached 22 weeks of age to verify the effects on their growth traits. The body weight of the improved Hinai-jidori chickens at 22 weeks was significantly greater than the conventional Hinai-jidori chickens. Moreover, the association between the SNP and body weights of Hinai-jidori chickens at market age (24 weeks) on the production farms showed that the A allele was significantly superior to the C allele. In conclusion, the CCKAR g.420 C>A SNP improves the growth rate of commercial Hinai-jidori chickens and could be a candidate marker for improving the growth performance in selective breeding of Hinai-jidori chickens.

The age-related changes of dietary phosphate responsiveness in plasma 1,25-dihydroxyvitamin D levels and renal Cyp27b1 and Cyp24a1 gene expression is associated with renal α-Klotho gene expression in mice.

In this study, we investigated the relationship between age-related changes in renal α-Klotho gene expression, vitamin D metabolism and the responsiveness of dietary phosphate in 1, 2 and 13 month-old mice fed a high phosphate (phosphate 1.2%) diet or low phosphate (phosphate 0.02%) diet for 5 days. We found that 1,25-dihydroxyvitamin D levels in plasma were significantly lower in the high phosphate group than the low phosphate group for 1 and 2 month-old mice, but not 13 month-old mice. In addition, in the high phosphate group plasma 1,25-dihydroxyvitamin D levels were decreased in 2 month-old mice relative to 1 month-old mice, but 13 month-old mice had higher levels than 2 month-old mice. In fact, plasma 1,25-dihydroxyvitamin D levels showed a significant correlation with vitamin D metabolism gene Cyp27b1 and Cyp24a1 mRNA expression in the high phosphate group. Interestingly, renal α-Klotho mRNA and protein levels were significant change with age. Furthermore, α-Klotho mRNA expression showed a significant negative correlation with plasma 1,25-dihydroxyvitamin D levels in the high phosphate group. Our results suggest that age-related alterations in renal α-Klotho expression could affect the responsiveness of dietary phosphate to vitamin D metabolism.